Adding my two cents: this is very probably an aircraft specific issue (in this case the default C172 G1000) and it doesn’t mean stall characteristics of the entire sim is broken. Two examples below in the 3rd party Carenado Seminole:
I can easily replicate in the default C172 G1000 what OP described in his original post, but I can’t do the same in Carenado Seminole.
In the words of Matt Nischan, one of the developers of the nearly “study-level” Working Title CJ4:
“There’s no conclusive observation that can be made by looking at one specific aircraft flight model configuration and then applying that conclusion to the entire flight simulation. How well a particular aircraft meets book values is entirely dependent on how well the flight model author adjusted the values to make the book values possible.”
Source: More Physics, More Real Winds - #256 by Bishop398
P.S 1: I am by no means implying that the issues mentioned by the learned OP should not be investigated.
P.S. 2: Carenado Mooney in MSFS exhibits almost the same stall characteristics as the OP described, and therefore a Mooney factory test pilot was consulted regarding the matter who testified by saying that the real Mooney and the one by Carenado exhibit almost the same stall characteristics.